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United States Patent |
5,591,339
|
Robinson
|
January 7, 1997
|
Self-cleaning filter screen for venturi suck back passage
Abstract
The invention is a filtering device for the drilled passage in on-off
control valves used in aircraft liquid crop spraying systems. The device
is mounted within the on-off control valve in the spray boom supply line
at the opening of the drilled passage which connects the low pressure area
of the suck back venturi to the spray boom supply line. In the "two-part"
and "four-part" configuration of the device, it is composed of a small
gauge wire mesh sleeve inside a perforated cylinder with raised collars on
both ends. The collars secure and align the device in the on-off control
valve assembly. The collars may be machined in one piece with the
perforated cylinder (the "two-part" configuration) or machined separately
and fitted onto the ends of the perforated cylinder (the "four-part"
configuration). In the "one-part" configuration, the device consists of a
cylindrical, open-ended, small gauge wire mesh sleeve mounted over the
machined portion of the on-off control valve where the drilled passage
meets the spray boom supply line.
Inventors:
|
Robinson; Webster (Rte. 1 Box 103 A4, Clayton, LA 71376)
|
Appl. No.:
|
515902 |
Filed:
|
August 16, 1995 |
Current U.S. Class: |
210/499; 244/136 |
Intern'l Class: |
B01D 035/02 |
Field of Search: |
210/498,499
55/306,312,498
244/136
|
References Cited
U.S. Patent Documents
3475883 | Nov., 1969 | Sullivan.
| |
3674154 | Jul., 1972 | Sicard | 210/499.
|
3701433 | Oct., 1972 | Krakauer et al. | 210/499.
|
3938586 | Feb., 1976 | Barlow et al. | 55/277.
|
4190217 | Feb., 1980 | O'Connor | 55/306.
|
4263140 | Apr., 1981 | Wujnovich | 210/499.
|
4514201 | Apr., 1985 | Brown | 55/433.
|
5113643 | May., 1992 | Peterson et al.
| |
5234592 | Aug., 1993 | Schneider | 210/499.
|
5482622 | Jan., 1996 | Stark et al. | 210/499.
|
Primary Examiner: Walker; W. L.
Claims
I claim:
1. In combination, a self-cleaning, open-ended filter screen and an
aircraft crop dusting system of a type having a fluid reservoir, a spray
boom connected to the wing of the aircraft, a supply line communicating
said fluid reservoir with said spray boom, a pump communicating with said
supply line for supplying fluid to said spray boom under pressure, a valve
assembly mounted in said fluid supply line between said pump and said
spray boom for controlling the flow of said fluid to the spray boom, a
recirculating line communicating with the fluid supply line between said
pump and said valve assembly for recirculating the fluid back into the
reservoir when the valve is in a closed position, an aspiration passage
communicating with said recirculating line and said fluid supply line,
said aspiration passage having an inlet between said spray boom and valve
assembly, whereby when the valve assembly is closed, fluid is drawn from
the spray boom through the aspiration passage back into said recirculating
line to the reservoir; said self-cleaning open-ended filter screen
comprising a wire mesh sleeve mounted in the fluid supply line between the
spray boom and valve assembly and communicating with said aspiration
passage, whereby foreign particles are filtered out of the fluid being
drawn from the spray boom, to thereby prevent blockage of said aspiration
passage, the filtered foreign particles being purged from the filter and
fluid supply line when the valve assembly is in an open position allowing
the fluid to flow to the spray boom.
2. The combination according to claim 1, wherein an annular space is
provided between said wire mesh sleeve and the inlet of said aspiration
passage.
3. The combination according to claim 2, wherein an open-ended perforated
cylinder surrounds said wire mesh sleeve, a collar connected to each end
of said perforated cylinder, each of said collars having a larger diameter
than said perforated sleeve, said collars engaging the interior wall
surface of said fluid supply line to provide a seal to ensure fluid flow
through the filter screen, the annular space and into the aspiration
passage when the valve assembly is closed.
4. The combination according to claim 3, wherein the collars are integral
with the perforated cylinder.
Description
CROSS-REFERENCE
There are no co-pending applications which relate to or involve this
device.
GOVERNMENTAL RIGHTS
The conception and development of this device did not result from federally
sponsored research or activities.
BACKGROUND
A. Technical Field
The present invention relates to an open-ended filter screen mounted in the
spray boom supply line of the on-off control valve assembly of aircraft
crop dusting spraying systems at the opening of the drilled passage which
connects the low pressure area of the suck back Venturi to the spray boom
supply line.
B. Description of Prior Art
The unwanted discharge of pesticides and other chemicals used during crop
dusting is a serious concern. Aircraft operators and landowners who spill
crop dusting materials onto the property of others or into surface waters
face substantial liability under state tort law as well as federal
environmental law. For example, some state and federal environmental laws
impose liability for pollution and personal injury even if an operator or
land owner is completely free of fault. Thus, there is a great need for
crop dusting systems which minimize such unwanted discharges.
An aircraft liquid crop spraying system is composed of several different
parts. The liquid which will be sprayed is stored in an internal hopper or
tank. The spraying equipment often consists of an assembly bolted to the
bottom of the hopper tank that supports a pump 2 and an on-off control
valve 9.
The liquid to be sprayed is forced from the hopper into the on-off control
valve 9 via a pump 2. When the on-off control valve 9 is open (FIG. 1),
the liquid passes through the valve 9 into a large strainer prior to
entering the spray boom. The spray boom is customarily attached to the
trailing edge of the wing by hangers fastened to the wing's frame. Nozzles
for atomizing the spray are placed along the boom on each wing. Each
nozzle has a spring loaded, diaphragm cutoff valve. The pump pressure
forces the diaphragm valves open, and the liquid is sprayed through the
nozzles.
When the on-off control valve 9 is in the closed position (FIGS. 2 & 8),
crop dusting fluids are recirculated 14 back to the hopper for agitation.
The recirculating fluid passes through a suck back Venturi 7 located in
the on-off control valve 9. The low pressure area of the Venturi 6 is
connected to the spray boom supply line 10 via a small drilled passage 1.
The drilled passage 1 allows fluid to be drawn from the boom into the low
pressure area 6 of the Venturi 7 during recirculation (FIG. 2).
Drawing fluid from the boom through the drilled passage 1 effectively
lowers the boom pressure and enables the diaphragm valves on the spray
nozzles to close quickly. In other words, the quicker the boom fluid
pressure drops, the quicker the spray nozzles close, thereby preventing
waste and environmental contamination caused by unwanted fluid discharges
during turns and ferrying.
Keeping the drilled passage 1 free of obstructions is critical to
preventing unwanted liquid loss. However, pesticides and other spraying
fluids often contain foreign particles such as rubber, glass, gravel or
dirt. As the fluid is being drawn from the spray boom through the drilled
passage 1 in the recirculating mode (FIG. 2), the foreign particles
present in the fluid often obstruct or block the drilled passage 1. This
blockage in the drilled passage 1 impedes the drop in boom pressure,
causing the nozzles to drip during turns or while ferrying.
Blockage in the drilled passage 1 can also combine with other problems to
cause unwanted fluid discharges. For instance, the on-off control valves 9
used in the industry typically employ a ball type valve 15. The placement
of the ball in the valve determines whether the fluid used enters the
spray boom or recirculates to the hopper for agitation after passing
through the suck back Venturi 7. Through extended use, however, the ball
and its corresponding seal often deteriorate and fail to provide a leak
proof seal. Thus, fluid enters the spray boom while the system is in
recirculating mode.
When the drilled passage 1 is clear, this fluid returns to the hopper via
the drilled passage 1 due to the low pressure area 6 created by the suck
back Venturi 7. When the drilled passage 1 is blocked, however, this fluid
accumulates in the spray boom. Eventually, the boom pressure reaches a
level sufficient to open the diaphragm valves causing unwanted discharge.
For the foregoing reasons, there is a need for an inexpensive device which
prevents particles in crop dusting fluids from blocking the drilled
passage 1 and causing unwanted and possibly unlawful discharges into the
environment. The invention resolves the above problems by ensuring that
the drilled passage 1 remains clear of debris. As will be shown below, its
chief features, which can be embodied in a number of forms, allow filtered
fluids 360 degree access to the drilled passage. Moreover, the inventions'
self-cleaning feature, which occurs during the spray mode, ensures
continuous access to both the drilled passage 1 and the spray boom.
SUMMARY
The present invention is a device which prevents the clogging of the
drilled passage 1, thereby avoiding the unwanted discharge of crop dusting
materials into the environment. The Self-Cleaning Filter Screen for the
Venturi Suck Back Passage 8 is an open-ended, filter screen that is placed
in the on-off control valve 9 assembly of existing aircraft liquid crop
dusting systems.
In the "two-part" and "four-part" configurations of the device (FIGS. 6 &
7), the perforated, filtering portion of the invention 12 has a narrower
diameter 3 than the spray boom supply line portion of the on-off control
valve 9, which allows free fluid flow to the drilled passage 9.
In the "one-part" configuration of the device (FIG. 8), a portion of the
on-off control valve 9 is machined ("the machined portion") 16 in the
spray boom supply line 10 around the opening of the drilled passage 1,
which provides the space 3 between the filtering portion of the invention
and the on-off control valve 9. In the "one-part" configuration of the
device, the device consists of an open-ended wire mesh sleeve 4 mounted
over the machined portion 16 of the on-off control valve 9.
The length and diameter of the invention vary with the type of on-off
control valve 9 used. Generally, all configurations of the device should
be constructed from a corrosion resistant, metallic substance such as
stainless steel.
In the "two-part" and "four-part" configurations of the device, the
non-perforated ends of the device are collared with a wider outside
diameter (FIGS. 6 & 7). This difference in diameter 3 seals and aligns the
filter 8 by fitting it snugly within the on-off control valve 9. FIG. 4
shows that the collar 11 closest to the spray boom assembly is wider than
the collar 11(a) closest to the hopper.
The perforations along the narrow, filtering portion of the device 12 are
lined with a 50 to 100 gauge wire mesh sleeve 4. The perforations 12 allow
for 360 degree fluid access to the drilled passage 1 and the wire mesh
sleeve 4 filters any foreign objects that might obstruct the drilled
passage 1. The device 8 is self-cleaning. Any trapped foreign objects are
purged through the system when the on-off control valve is open (FIG. 1).
This device can be applied to any system which employs a passage accessing
the low pressure area 6 of a Venturi 7. In summary, when properly
installed, the device eliminates nozzle dripping when the on-off control
valve is in the closed position (FIG. 2). The device conserves material
and prevents unwanted and possibly unlawful fluid discharges.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features, aspects, and advantages of the present invention
will become better understood upon reading the following detailed
description in conjunction with the accompanying drawings:
FIG. 1 shows an exposed view of the on-off control valve 9 in which the
Self-Cleaning Filter Screen 8 is placed. This diagram also displays the
fluid path of the crop spraying substance while the on-off control valve
is in open (spray) mode;
FIG. 1A shows the combination of the screen and crop dusting system mounted
on an aircraft.
FIG. 2 shows an exposed view of the on-off control valve 9 in which the
Self-Cleaning Filter Screen 8 is placed. This diagram also displays the
fluid path of the crop spraying substance while the on-off control valve
is in recirculating mode;
FIG. 3 shows an ordinary view of the invention 8 and a typical on-off
control valve 9 in which the Self-Cleaning Filter Screen 8 is placed. This
diagram also shows the location of the drilled passage 1 within the on-off
control valve 9;
FIG. 4 shows a side view of the "two-part" and "four-part" configurations
of the Self Cleaning Filter Screen;
FIG. 5 shows the top and bottom view of the "two-part" and "four-part"
configurations of the device. This diagram also shows that the Self
Cleaning Filter Screen 8 is open-ended;
FIG. 6 shows an exploded view of the Self-Cleaning Filter Screen 8 in the
"two-part" configuration;
FIG. 7 shows an exploded view of the Self Cleaning Filter Screen 8 in the
"four-part" configuration; and
FIG. 8 shows an exposed view of the on-off control valve 9 in the
"one-part" configuration of the device in which the Self-Cleaning Filter
Screen 8 consists of a fine wire mesh screen 4 mounted over the machined
portion 16 of the on-off control valve 9. This diagram also displays the
fluid path of the crop spraying substance while the on-off control valve
is in the closed (recirculating) mode.
DESCRIPTION OF THE INVENTION
A. Definitions
Drilled Passage 1--That portion of a typical crop spraying on-off control
valve 9 which connects the low pressure portion 6 of the suck back Venturi
7 with the spray boom supply line 10 for the purpose of rapidly lowering
of boom pressure causing the spray nozzles to close quickly when the
on-off control valve 9 is in the closed position (FIG. 2).
On-Off Control Valve 9--A valve that either allows crop dusting fluids to
flow from the hopper to the spray boom or closes off the spray boom and
recirculates the fluids back to the hopper (FIGS. 1 & 2).
Suck Back Venturi 7--A typical Suck Back Venturi is comprised of two
truncated cones connected by a short throat, and it is located in the
recirculating line 14 of the on-off control valve 9.
B. Detailed Description of the Elements
The device 8 is composed of either one (FIG. 8), two (FIG. 6) or four (FIG.
7) component parts, and it is easily constructed. In either configuration,
the Self-Cleaning Filter Screen 8 has generally the same shape and
functions exactly in the same manner. In the "two-part" and "four-part"
configurations, the central portion of the cylinder 12 is narrower or
smaller in diameter than the two ends forming collars 11 & 11(a), which
create a space 3 between the outer diameter of the perforated cylinder 12
and the interior diameter of the spray boom supply line 10 portion of the
on-off control valve assembly 9. The collars 11 & 11(a) at the ends of the
perforated cylinder 12 properly secure and align the device in the on-off
control valve 9 and maintain a uniform distance 3 between the opening to
the drilled passage 5 and the perforated cylinder 12.
In the "two-part" and "four-part" configurations of the device, the
perforated cylinder 12 which covers the wire mesh sleeve 4 is perforated
uniformly around the entire circumference of the cylinder. These holes 13
allow fluid to return to the hopper from the spray boom via the drilled
passage 1.
The interior circumference of the perforated cylinder 12 is lined with a
small gauge wire mesh sleeve 4. This wire mesh filters the fluid which
passes through the perforations before it enters the drilled passage 1.
Since the ends of the device 8 are not covered by the wire mesh 4,
filtered foreign particles are purged through the system during the spray
mode (FIG. 1), which makes the device self-cleaning.
In the "two-part" configuration (FIG. 6), the device 8 is principally
comprised of a perforated cylinder 12 and a small gauge wire mesh sleeve
4. This configuration can be constructed by machining the collars 11 &
11(a) and the perforated cylinder 12 in one piece with a narrower outside
diameter for the perforated cylinder 12.
In the "four-part" configuration (FIG. 7), the collars 11 & 11(a) are
separately machined sleeves, which fit over each end of the perforated
cylinder 12. These collars 11 & 11(a) have an interior diameter slightly
larger than the exterior diameter of the perforated cylinder 12. In this
manner, the collars 11 & 11(a) fit snugly on the ends of the perforated
cylinder 12. In this version of the device 8, the perforated cylinder 12
need not be machined as it is sealed off by the collars 11 & 11(a).
In the "one-part" configuration of the device (FIG. 8), the on-off control
valve is machined 16 around the opening of the drilled passage 1 where it
meets the spray boom supply line 10, creating a space between the device
and the on-off control valve. In this configuration, the device only
consists of a cylindrical, open-ended, small gauge wire mesh sleeve 4. The
device need not be collared or have a perforated cylinder 12 covering the
filter screen 4, because the space needed for filtering 3 is provided by
the machined portion 16 of the on-off control valve 9.
D. Advantages of the Invention
The previously described versions of the invention have many advantages
including its inexpensive and simple construction as well as its easy
incorporation into existing aircraft crop spraying systems. Additionally,
the present invention provides a cost effective resolution to serious
economic and environmental concerns. As a practical matter, the device is
easily constructed from readily available materials. These materials
include corrosion resistant wire mesh and tubing. The manufacturing
process is also straight forward and simple.
The length and diameter of the invention may vary with the specifications
of the on-off control valve used. The device need not be removed once
installed as the invention is self-cleaning and not susceptible of wear
and tear. Installation is simple as the device need only be placed in the
portion of the on-off control valve leading the spray boom. The invention
may be held in place by friction, a rivet, a tack weld or other similar
means.
Although the present invention has been described in considerable detail
with reference to certain preferred versions, many other versions are
possible. For example, a variety of materials including non-ferrous metals
such as aluminum and man-made substances such as plastic or composites can
be used to construct the device. Additionally the device can be easily
adapted to almost all on-off control valve types which employ a suck back
Venturi and drilled passage accessing the low pressure area. The device
offers immediate and permanent relief from the previously described
difficulties.
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